# Quantum Lunch: Pattern formation in biological systems & Electroweak baryogenesis in 2HDMs – University of Copenhagen

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# Quantum Lunch: Pattern formation in biological systems & Electroweak baryogenesis in 2HDMs

Speaker: Nils Hermansson Truedsson, Dep. of Astronomy and Theoretical Physics, Lund University.

Full Title: Pattern formation in biological systems & Electroweak baryogenesis in 2HDMs -- A brief review of two theses in theoretical physics

Abstract: In this talk I will briefly review my two theses (bachelor and master) in the fields of theoretical biophysics and theoretical particle physics.

The first of these concerns the formation of smooth quasi-periodic patterns in static discrete so-called reaction-diffusion (RD) systems, which are of particular interest to biology. RD systems are governed by a modified diffusion equation, in which a term corresponding to reactions has been added. As the smoothness of the sought patterns can be attributed to the integrability of the systems in question, only reaction terms allowing for conserved quantities are wanted. Thus, there is interest in knowing the restrictions on the forms of the added terms allowing for such quantities and corresponding patterns. A one-dimensional method for systems with one so-called species was known beforehand, but it was found that a generalization of the method to higher dimensional systems is not possible. However, the method can be generalized for a one-dimensional system with an arbitrary number of species. As an example, quasi-periodic patterns for a system of two species were found explicitly.

The second thesis concerns the observed baryon asymmetry of Universe (BAU), and how to explain it through so-called electroweak baryogenesis (EWBG) in Two-Higgs-Doublet Models (2HDMs). 2HDMs are minimal extensions of the Standard Model (which on its own cannot explain the BAU in terms of EWBG) in which a second scalar $SU(2)_{L}\otimes U(1)_{Y}$ doublet is added. The effects of adding such a doublet are, among other things, additional sources for CP-violation, a richer electroweak symmetry breaking and five Higgs bosons instead of one. Since the parameters in the 2HDM Lagrangian density in general may have arbitrary values, the parameter space of the models in question must be examined in light of experiments and certain conditions from EWBG. As this project is to be finished in May 2016 there is work left to do and results yet to be obtained, but, important steps along the way have already been made and the final goal is in reach.